The move by Lord Justice Goldring, the senior presiding judge in England and Wales, follows the threat of a high court legal challenge and accusations from Tory, Labour and independent candidates that he was "usurping the role of parliament" and had acted without consultation.

The U-turn came after a second candidate was forced to withdraw because of a minor juvenile offence committed at the age of 14 nearly 50 years ago. Alan Charles Labour's official candidate for the post in Derbyshire, said the offence, for which he was given a conditional discharge, barred him despite the fact that he has been the vice-chair of Derbyshire police authority for the past three years.

Goldring's ruling is believed to have hit about a dozen of the 130 declared candidates for the 15 November elections, including six or seven Conservatives in winnable contests, including Kent, Surrey and Wiltshire.

The judge said he had decided "not to press" his guidance that magistrates had to resign as soon as they were named as candidates, "given that several serving magistrates were selected" before his original decision.

His revised guidance says that for this first round of elections, as long as they undertake not to sit on the bench while the campaign is in progress, candidates will not have to resign as JPs unless they are elected.

His retreat in the face of overwhelming criticism lifts the threat of a legal challenge that could have derailed the timetable for the elections.

But there were no signs on Friday of a similar U-turn by the Home Office over the stringent rules on past convictions in the elections.

Charles, the second candidate to be barred, told the Guardian he could not even remember the precise details of the charge he faced in 1965 for the non-violent offence, but had declared it to the local force when he was vetted three years ago.

"It was dealt with at the time and went through the judicial process. If it happened today, it would probably be resolved through a restorative justice process. The bizarre thing is that you can be prime minister, home secretary or the police minister or a member of the House of Lords but not a police commissioner candidate," he said, adding that there was no record of his conviction on police databases.

Bob Ashford, Labour's candidate in Avon and Somerset, had to stand down on Wednesday because of a minor juvenile offence he committed when he was 13 in 1966.